Try executing the following code, which creates a rectangular array of
points extending from n=0 to n=nn horizontally and m=1 to m=nn
vertically:
Do[
Print["nn = ", nn];
Show[
Graphics[
Table[Point[{n, m}], {n, 0, nn}, {m, 1, nn}]]], {nn, 5,8}]
Then click on the plots to show the bounding boxes.
For nn<=6 the bounding box is closely wrapped around the array, with the
bottom line especially located just a little below the m=1 row.
For nn>=7 the bottom of the bounding box suddenly drops down one unit
and is now located a little below where an m=0 row would be, if there
were one.
If you make the array run only from n=1 and m=1 in both directions, the
bounding box wraps tightly all around for nn<=6, but drops back by one
unit on both left and bottom sides for nn>=7.
Try giving a larger PointSize to the points. If the points are large
enough the circular points on the outer boundary of the array get cut
off by the bounding box on all 4 sides for nn<=6, but only on the top
and two sides, not on the bottom, for n>=7.
Same thing happens with Circle or Disk -- except bounding box always
expands enough so the circles or disks are never cut off.
Not a serious bug, maybe -- but does produce some minor hassles, e.g.,
if you're exporting a series of figures at increasing values of nn to go
into another application, and counting on the bounding boxes to be all
the same size.
[Mathematica 4.0, Mac PB G3, OS 8.6]